U.S. patent number 4,949,066 [Application Number 07/191,383] was granted by the patent office on 1990-08-14 for circuit arrangement for transmitting a supply voltage and a control signal.
This patent grant is currently assigned to Mannesmann Rexroth GmbH. Invention is credited to Peter Reinhardt.
United States Patent |
4,949,066 |
Reinhardt |
August 14, 1990 |
Circuit arrangement for transmitting a supply voltage and a control
signal
Abstract
With the invention a supply voltage and a control signal are to
be supplied via a two-conductor cable to the power stage of a
solenoid valve. For this purpose pulse-width modulation is
employed, i.e. in a microcomputer the adjusting signal is converted
directly as pulse-width-modulated signal via a power stage to an AC
voltage. The control signal is obtained from the pulse width in the
power stage.
Inventors: |
Reinhardt; Peter (Lohr,
DE) |
Assignee: |
Mannesmann Rexroth GmbH (Lahr
Postfach, DE)
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Family
ID: |
6328162 |
Appl.
No.: |
07/191,383 |
Filed: |
May 9, 1988 |
Foreign Application Priority Data
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May 22, 1987 [DE] |
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3717260 |
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Current U.S.
Class: |
73/25.05;
307/107; 340/12.33; 340/310.12; 73/31.05 |
Current CPC
Class: |
G08C
19/22 (20130101) |
Current International
Class: |
G08C
19/22 (20060101); G08C 19/16 (20060101); H04M
011/04 () |
Field of
Search: |
;340/31R,31A,31CP
;364/492 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0226844 |
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Nov 1986 |
|
EP |
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2260916 |
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Jun 1974 |
|
DE |
|
2848595A1 |
|
May 1980 |
|
DE |
|
2949237A1 |
|
Jun 1980 |
|
DE |
|
3543073A1 |
|
Jun 1987 |
|
DE |
|
Primary Examiner: Orsino; Joseph A.
Assistant Examiner: Hofsass; Jeffery A.
Attorney, Agent or Firm: Harness, Dickey & Pierce
Claims
I claim:
1. Circuit arrangement for transmitting a supply voltage and a
control signal via a cable to a power stage for driving a solenoid
valve, characterized by a changeover contact in said circuit for
switching the polarity of the DC supply voltage alternately between
two conductors of said cable to create pulses, the duration of said
pulses being modulated in dependence upon the adjusting value of
said control signal, and said power stage including a full-bridge
rectifier for reestablishing the DC supply voltage from said pulses
and a desired value generator for reestablishing the control signal
in response to the duration of said pulses.
2. Circuit arrangement according to claim 1, characterized in that
the desired value generator consists of a low-pass filter.
3. Circuit arrangement according to claim 1, characterized in that
the desired value generator consists of a timing member measuring
the pulse duration.
Description
The invention relates to a circuit arrangement for transmitting a
supply voltage and a control signal according to the preamble of
claim 1.
Solenoid valves, in particular proportional valves, are driven via
an electric amplifier as power stage to which a desired value
control signal is supplied which is calculated remote from the
power stage in a microprocessor control and is first in the form of
a digital signal, being converted with the aid of a digital-analog
converter to an analog signal which is conducted as control signal
via a cable to the power stage in which from the analog signal a
digital signal is again derived for driving the magnet of the
valve. The desired value control signal transmitted via the cable
usually has an amplitude of .+-.10 volts.
In addition, via a cable a supply DC voltage, as a rule of 12 volts
or 24 volts, must be supplied to the power stage. Thus, hitherto
two separate cables each having two conductors were necessary, and
the cable for the control signal had to be made shielded to avoid
leakage. Also, a digital-analog converter is a relatively expensive
component.
The invention is based on the problem of simplifying the signal and
supply voltage transmission.
The problem is solved according to the invention by the features in
the characterizing clause of claim 1.
The supply voltage is thus transmitted in the form of a
pulse-width-modulated signal. The full supply voltage is obtained
again by the rectification in the power stage. On the other hand,
the pulse width is a measure of the desired value control signal.
Thus, it is possible with the invention to transmit the supply
voltage and the desired value control signal via a two-conductor
cable. In addition, the conversion of the digital output signal of
the microprocessor to the analog value to be transmitted is
eliminated.
Advantageous further developments of the invention are
characterized in the subsidiary claims.
An example of embodiment of the invention will be explained in
detail hereinafter with the aid of the single Figure of the
drawings in which a circuit diagram of the circuit arrangement is
shown.
The circuit arrangement consists of a changeover or two-way contact
10, a two-conductor cable 11 and a power stage which consists of a
full-bridge rectifier 12, a desired value generator 14 and an end
stage 15, by which the proportional magnet of a valve, not
illustrated, is shown. The two-way contact 10 is indicated in the
drawing only schematically and consists of two changeover switches
17 and 18 which are actuated by a digital control signal which is
furnished by a microprocessor, as shown, and which represents the
desired value of the current for the proportional magnet. Circuit
details of the changeover contact means 10 are not shown. The
changeover switches 17 and 18 are switched so that they alternately
connect one conductor 19 or the other conductor 20 of the cable 11
to the positive pole or to the negative pole of a voltage source 22
which furnishes the supply voltage.
Thus, the supply voltage is modulated by the changeover switches 17
and 18 in dependence upon the digital value of the control signal.
This gives a pulse-width-modulated circuit in which for example the
width b of the positive pulse portion is proportional to the
magnitude of the control signal. During the intervals between two
positive pulse portions the polarity of the conductors 19 and 20 is
interchanged and the negative portion of the supply voltage thus
transmitted.
In the full-bridge rectifier 12 at the receiving location, i.e. at
the end of the cable, the supply voltage is reestablished in that
the negative and positive portions are again combined to give a DC
voltage which is supplied to the end stage 15.
In addition, the voltage is tapped off in front of the rectifier 12
and supplied to the desired value generator 14 in which the control
signal is again formed which is likewise supplied to the end stage
15.
With the aid of a low-pass filter 14, not shown, the desired value
can be converted to a DC voltage having an amplitude which is again
proportional to the pulse width b. The low-pass filter necessarily
results in a phase displacement and a residual ripple of the
control signal.
If this is to be avoided another possibility is to measure the
pulse widths in the desired value generator 14 and to generate the
desired value quantity in dependence upon the duration of the
pulses. This has the advantage that on every sampling of a pulse
the actual value is determined. In addition, by measuring the
interval time the measurement of the pulse times can be
checked.
In the prior art numerous circuits are known for changeover or
two-way contacts driven by a digital signal and circuits generating
from a pulse width of a digital signal an analog amplitude
value.
In the end stage 15 in known manner a current stabilization is
carried out irrespective of the resistance change of the
magnet.
* * * * *